You know the idea that eventually we'll be able to download our
brains/personalities to computer, to achieve physical immortality?

There is a big trouble with this version of the immortality thing that
people rarely mention. You go to the scanning and uploading center one
day and write them a check. They scan and upload your brain, and say
"All done, time to go home!"

"That's it?" you say. "I don't feel any different."

"Well, of course not. You're no different. But the uploaded
version is immortal."

Then you go home and grow old, and every once in a while you get an
email:

From: Mark Dominus (Immortal version) <mjd@forever.org>
Subject: Wish you were here
Having a great time here in paradise! Haven't aged a day.
Thanks!

Or maybe one like this:

From: Mark Dominus (Immortal version) <mjd@forever.org>
Subject: Guess what I just did?
Today I had sex with Arthur C. Clarke while swimming in a
giant hot-fudge sundae. It was totally awesome! Too bad you
couldn't be here. I know exactly how much you would
have enjoyed it.
Sorry to hear you're sick. Hope the chemo works out.

Then you die, and some computer program somewhere simulates the
immortal version of you having a little ritual observance to mark your
passing.

Sometimes the proponents of this scheme try to conceal this enormous
drawback by suggesting that they obliterate the original version of
you immediately after the upload. Consider carefully whether you
believe this will improve the outcome.